Acta Physico-Chimica Sinica ›› 2020, Vol. 36 ›› Issue (8): 1905047.doi: 10.3866/PKU.WHXB201905047

• Article • Previous Articles     Next Articles

Catalytic Oxidation of Toluene Over Potassium Modified Mn/Ce0.65Zr0.35O2 Catalyst

Xiaoxiao Lai1, Jie Feng2, Xiaoying Zhou1, Zhongyan Hou1, Tao Lin1,*(), Yaoqiang Chen1,3,*()   

  1. 1 College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
    2 College of Chemical Engineering, Sichuan University, Chengdu 610064, P. R. China
    3 Sichuan Provincial Environmental Catalytic Material Engineering Technology Center, Chengdu 610064, P. R. China
  • Received:2019-05-13 Accepted:2019-07-02 Published:2020-05-19
  • Contact: Tao Lin,Yaoqiang Chen E-mail:lintaochem@scu.edu.cn;chenyaoqiang@scu.edu.cn
  • Supported by:
    National Key Research and Development Program of China(2016YFC0204901)

Abstract:

Volatile organic compounds (VOCs) are both harmful to human health and the environment; however, catalytic combustion offers a promising method for VOC purification because of its high efficiency without secondary pollution. Although manganese-based catalysts have been well studied for VOC catalytic oxidation, their catalytic activity at low temperature must be improved. Alkali metals as promoters have the potential to modulate the electronic and structural properties of the catalysts, improving their catalytic activity. Herein, a Ce0.65Zr0.35O2 support was prepared by co-precipitation and MnOx/Ce0.65Zr0.35O2 catalysts were obtained through the incipient-wetness impregnation method. The catalytic properties of K-modified MnOx/Ce0.65Zr0.35O2 for toluene oxidation with different molar ratios of K/Mn were investigated. In addition, the catalysts were characterized by XRD, UV/visible Raman, Hydrogen temperature program reduction (H2-TPR), Oxygen temperature programmed desorption (O2-TPD), X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance FTIR spectroscopy (DRIFTS) experiments. The results showed that alkali metal doping with K significantly improved the catalytic activity. In particular, when the molar ratio of K/Mn was 0.2, the monolith catalyst Mn/Ce0.65Zr0.35O2-K-0.2 exhibited the best performance with the lowest complete conversion temperature T90 of 242 ℃ at a GHSV of 12000 h−1. The XRD results suggested that MnOx was uniformly distributed on the surface of the catalyst and that Mn4+ partially reduced to Mn3+ on the addition of K. The Raman spectrum demonstrated that with increasing K content, both the β- and α-MnO2 phases coexisted on the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst, increasing the number of surface defect sites. The H2-TPR experiment results confirmed that Mn/Ce0.65Zr0.35O2-K-0.2 exhibited the lowest reduction temperature and good reducibility. From the O2-TPD experiments, it was clear that Mn/Ce0.65Zr0.35O2-K-0.2 contained the most surface adsorbed oxygen species and excellent lattice oxygen mobility, which benefitted the toluene oxidation activity. In addition, the XPS results suggested that the content of surface adsorbed oxygen species of the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst was the highest among all the tested samples. In addition, toluene-TPSR in N2 as measured by in situ DRIFTs analysis demonstrated that available lattice oxygen was present in the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst. Therefore, the Mn/Ce0.65Zr0.35O2-K-0.2 catalyst exhibited the best redox properties and oxygen mobility of the prepared samples and showed excellent activity toward toluene oxidation. Therefore, it was concluded that the addition of an appropriate amount of K improved the redox performance of the catalyst and increased the number of surface defect sites and mobility of the lattice oxygen of the catalyst as well as the concentration of the surface active oxygen species, thereby significantly improving catalytic ability.

Key words: Toluene, Catalytic oxidation, Potassium, Ce0.65Zr0.35O2, Manganese oxide

MSC2000: 

  • O643